Reversal of Ross Sea shelf water freshening is linked to a persistent decline in Antarctic sea ice since the mid-2010s

Abstract Since the mid-2010s, a sharp rebound in dense shelf water (DSW) salinity has been observed in the Ross Sea, coinciding with a persistent decline in sea ice around Antarctica. Despite extensive scientific study and significant attention given to these two phenomena due to their potential influence on Earth’s changing climate, a physical link between them has yet to be established. Here, by examining atmospheric circulation in response to shifts in major climate variability modes before and after these dramatic changes, we showed that a combination of large-scale circulation patterns drove both the decline in Antarctic sea ice and the increase in Ross Sea DSW salinity. After the mid-2010s, climate-driven atmospheric circulation generated anomalous northerly winds across much of the high-latitude Southern Ocean. However, the Ross Sea sector uniquely experienced strengthened southerly flow of cold continental air. Consequently, this process led to enhanced sea ice loss around Antarctica through warmer air advection from the north, yet simultaneously, expanded the Ross Sea polynyas, enhancing sea ice formation and contributing to increased Ross Sea DSW salinity. Our findings, therefore, establish a robust linkage between these two Southern Ocean transitions, highlighting their interdependence driven by large-scale climate modes.